Tractor-trailer braking system



E. R. PRICE TRACTOR TRAILER BRAKING SYSTEM Oct. 30, 1945.

Filed June 5, 1944 2 Sheets-Sheet l INVENTOI? EARL PIP/CE rron/vs) r E.R. PRICE TRAGTOR- TRAILER BRAKING SYSTEM Oct. 30, 1945.

Filed June 5, 1944 2 Sheets-Sheet 2 compressible one.

Patented Oct. 30, 1945 2,387,942 TRACTOR-TRAILER BRAKING SYSTEM Earl R.Price. South Be Bendix Aviation Corporation,

nd, Ind., assignor to South Bend, 11113.,

a corporation of Delaware Application June 3, 1944, Serial No. 538,643

4 Claims.

This invention relates to tractor-trailer braking systems, wherein theentire system is under the control of a single manually operable memberlocated on the tractor.

It is contemplated that both the tractor and trailer brakes shall beoperated hydraulically. This diners from the conventionaltractor-trailer brakin system primarily in substituting hydraulic brakeson the trailer'for the customary vacuum' or air brakes. An advantagederived from using hydraulic brakes on the trailer is improvedsmoothnessand better control, due to the use of an incompressible fiuid in placeof a The operator has a better sense of control over the trailer brakes,and the efficiency of the system is increased.

Where hydraulic brake operating motors on the trailer are added to thosealread present on the'tractor, the displacement of fluid required tooperate the brakes is greatly increased. In proposals heretofore madefor using hydraulic trailer brakes, either this problem has not been metat all, or it has been met by substituting an entirely .new tractorhydraulic system for the conventional one.

/ An object of the present invention is to provide, under the control ofthe conventional master cylinder on the tractor, a hydraulic brakesystem having adequate displacement for both the tractor and trailerbrakes.

A further object of the present invention is to provide a mastercylinder actuated conjointly by power and manual effort and capable ofoperating both tractor and trailer brakes, which master cylinder iscontrolled by the operation of a relatively small conventional mastercylinder on the tractor. 1

Other objects and advantages of the present invention will becomeapparent during the course of the following description, reference beinghad therein to the accompanying drawings, in which:

Figure 1 is a diagrammatic showing of a tractor-trailer braking systemincorporating my invention;

Figure 2 shows in outline the coupling unit which connects the tractorbraking system to the trailer braking system;

Figure 3 is a section pling unitof Figure 2;

Figure 4 is a section taken through the power and manually operatedmechanism for actuating the combined tractor-trailer hydraulic brakingsystem; and

Figure 5 is a section taken on the line 5-5 of Figure 4.

Referring to Figure 1, a tractor vehicle is indicated generally at l2and a trailer vehicle at l4. The trailer is provided with a pair ofbrakes indicated diagrammatically at l6. Each of the trailer brakes isprovided with a hydraulic m0- showing part of the couthe tractor or of amaster cylinder 54.

tor l8 for actuating the brake in the well known manner. The hydraulicmotors l8 are connected by means of conduits 20 and 22 to a coupling 24,which interconnects the tractor and trailerhydraulic systems.

Referring to Figure a master cylinder 26, tional construction. cludes areservoir portion 28, which is adapted to supply fluid to the trailerbrake system through the conventional compensating port when the pistonof the master cylinder 26 is in released position. The piston of mastercylinder 26 is mechanically connected by means of a rod 30 with thepiston 32 (see Fig. 3) of a hydraulic motor 34 which is removablycoupled to the master cylinder 26. A spring 36 may tween piston 32 andthe wall of motor 34 in order to normally retain the piston in releasedposition. In released position of said piston, it may rest a ainst 2,the coupling comprises which may be of convencylinder 26, in order thata U-shaped locking be used to couple the motor and With this arrangementthe hyyoke may master cylinder. draulic system of cates with the motor34 is connected by mechanical means only wit-h the piston of the mastercylinder 26, which is locatedon the trailer and in communication withthe trailer brakes. Therefore, when it is desired to disengage theparticular tractor from the particular trailer, the motor 34 and mastercylinder 26 may be uncoupled without the loss of fluid from the system.Either the trailer may thereafter be coupled with another vehicle in asimilar manner.

Chamber 44 of motor 34 is connected by means of conduit 52 with theoutlet or discharge end The master cylinder 54 is also connected bymeans of a conduit 56 with a pair of hydraulic motors 58 which arearranged to operate the rear brakes of the tractor vehicle, showndiagrammatically at 60. Furthermore, master cylinder 54 is connected bymeans of conduits 62 and 64 with a pair of hydraulic motors or wheelcylinders 66 which are arranged-to operate the front brakes of thetractor vehicle, shown diagrammatically at 68.

The master cylinder 54, which is sufiiciently large, in length and incross section, to displace fluid for actuating both tractor and trailerbrakes, is operated by a combination of manual and the means forcreating pressure therein is illus- This master cylinder inbe locatedbei may be prothe tractor which communi- 2 a Y asazaae trated in Fig. 4.Said master ,cylinder'vhas a large :Plston '12: is therefore :moved.forward .convolume bore. 10, inwhich a pistong'l- Z is reciprojointly bythe power: createdipressureof power cable. A liquid reservoir '11,:located above the: cylinder and-:themanually'created:pressurebore 10,is adapted to supplyfluidito the hydraulic oi! master cylinder 9!- to:displace nine under system to compensate forxchanges in-volume of apressure-throughconduits '52, and 162mmap the liquid therein, saidreservoir being i'n :com-- ply: the-:tractorand trailer brakes. -Inthe'case munication with bore 7H1 by means of ccmpensaoifthetractorxbmkeglthe conduits {Gland-M ats tion port 16, and passage Ti-through piston-. 71, ;in:.dire.ct;commu-" so long as roddfl: remainsinretracted; positi'om V Rod 80 isadapted to beamovedrforwardto firstclose the passage through piston 12', and their sure on rod ljfl beingdevelopedsbynmeans afar motor-214%and mas'ten'cylipdertlii. pressuredifierential'. created ,over the tandem" lAs-a pressure"differentiallisdevelopedover the pistons 82 and 84, and: additionallysby meanseofpistons- :of .power' :cyllnd'er -30; a corresponding hydraulicpressurercreated in expansiblescham pressure-gdilferentialsis'ibuilt. upover diaphragm ber 86 and acting against a pistQnE.8' which is 110;.This-.-results il'll a: reaction vforce acting. mechanically connectedtend-18mg Flor a: more through piston' liuhagainst the pressurer-devebcomplete description of "structureland operoped byjthe. operator: inchamber 1170. As the ation of master cylinder 5!, power' cylinder '90:20' ditlerentialaover the power cylinder pistons in- (which houses thepistons-82 andlll) andzex. creases-,gthe difl'rential-nver diaphragmllll also pansible chamber '86, reference may ibe rhadito increases,thereby developing a progressively in the application of Thomas. andPrice; Seri'aLNo; creasing: reaction force which lindicatescto the-504,854, filed October 4, .1943, wherein-Figures: 1 operator the extent.of' brake application; The 2"? operator: isfurther iniormedxas tothe-extent of closed in the present application. I :brake applicationbecause it is-necessary for him Figure 5 is a sectional view of thevalvemeans tofollow up with pedal? inrorder to displace 92 which controlsoperation of power cylinder v additionallfiuidtozchamberslfias.pistonzu'moves 90. Reference may also be had to theaforeonithewpressure: stroke; Therefore; unless .the said applicationSerial No. 504,-85 4to ,obtaina operator:continuesutodisplace'ifiuidifrom master detailed description Of'thevalve 92 and: itsiopcylinderflandcontinues=to increase the'm'anualeration. forceappliedl-to-pe'dai'z' flyvalve" element Ml will Aconventional master cylinder located in returnito -itsseatilbringingothe valve mechanismthe tractor I2, and operatedby-themsualkbrake: tolappedpcs-itibm. ;In ,=1this position; the 'brakepedal 96 is connected by means oftamconduit 98- branch conduit I02.connects master cylinder 8) operator either depressesc thepedal furtheror to the expansible chamberlfi. releases-- it. Wham the operatorreleases: the Master cylinder '94'is provided with the usual manuallyapplied-pressure; diaphragm I10 iwilll liquid reservoir l0. ,=whichsuppliesefluid to the bezmoved .away-'fromvalve eIemenirJ'UEby'meansconduits 98 and 102.; during-the time when xnas.-- 101' spring: 122;:andithewpressure differentials over --ter cylinder 9% remains inreleased or retracted the pistonsuinnthe power-cylinder will be de--position. 1;, stroyedi.therebyipemiittinrsncings lumen When theeoperatordesiresztozactuateathetrace 45, to return thepower-'spistonssandsplatonffi to retorfand trallerlbrakes, hedepressesrthe pedal 96', leased positiom Fluidwimbf; coume-rflorwibcckcreating pressure in master cylinder394, and orc-- 'fromth'e brakestocyllnderglflila'ndlthe hydraulic ing liquid therefrom both toexpansible chamber systemiwillbe restorediitoitsozieinallstatus.

86 and the valve operating chamber mu; ,e The From the above, it-wilrbeappreciated-that: 1" pressure of fluid in chamber 86 acts againstpishaye provided a power and manually operated ton 88 creating a directpressure on rod 8!! tendhydraulic master cylinder 5! having suthcient mgto move the same forward to first close pasfluid displacement to operateboth tractor and sage 18 and thereafter move piston 12 on its trailerbrakes, which is itself controlled by a pressure stroke. Itv will benoted that the rdi-- manually:operatedkmastencylinder havingrlmuchameter of piston 88; or in-otherwords itsz-effeclessathamtherequiredkldisplacementl l l"ev er'thet tive cross sectional area, ismuch-less-thant-hat less-; there;-is noldangertoffailurewof-thei'bralies; of piston 12. This is,necessarybecause-the:mane duee-toefbottomingroftheipistcmih';the-manually uallyoperated master cylinder 9!. has a relative1y operatedmastercylindertsmall volume. whereas the master :cylinder- .541 Although:a:particular'embodimenti of my inmust have a volume suilicient to applyboth trac- .vention has been described", it will be. understood tor dtri e br e by those: skilledln. trier-art.tliatil-tliewobiectvof the Atthe same time pressurewfluid-enteringchame inventiommay'be:attain-edbythezuseoficonstruc ber I 00 in t e valve device =82moves'piston.I05 'tions v difi'enent in. certain. respectsfromz'thatidi's tov the right (as seen in :Flgure 5), first seatingclosed. without: departing from the underlying fold) and subsecuentlymoving poppetf l5If4 'from': modifications which substantially theresults its seat toadmit. air atatmospheric: pressure-to otrzmyinvention:maywbenobtained::throush the said chambers H0. and H2.-Since-the'chamberss use: of substantially the same: or equivalent: H6and III, which are-aheadiof the a-respective: m-eans.

pistons 84 and 82, remain. connected tostheavac" -.Ilclaim:;

uum source, a pressure diflerential is -createdrover 1. A. powerbraking! systema'for a tractor: and pistons 82 and 8.4;movingvthemwtowardr-therighttrailervehicle'combinationz.comprising-brakes-on (as seen in Fig. 4-),thus-greatlyincreasing. the 'thetractor; ,hydraulic meansfor:operatinptlie: 'i'ong pcting through rodLW-against"piston-'12; tractorbrakes; brakes: o the trailer hydmulic means for operating the trailerbrakes, a large displacement master cylinder operatively connected toboth of said hydraulic means, said master cylinder having sufilcientdisplacement to operate both tractor and trailer brakes, a powercylinder adapted to create pressure in said master cylinder, valvemechanism controlling said power cylinder, a hydraulic motor operatingsaid valve mechanism, a manually operable low displacement, mastecylinder in communication with said motor to actuate the same, anexpansible chamber also in communication with said manually operablemaster cylinder, said expansible chamber being operatively associatedwith the large displacement master cylinder in such a way that thepressure of liquid in the expansible chamber increases the pressure inthe large displacement master cylinder and the volume of the expansiblechamber increases proportionately to the decreasing volume of the largedisplacement master cylinder, a compensating passage associated with aliquid reservoir and in communication with the manually operable mastercylinder when the piston of the same is in retracted position, and asecond compensating passage independent of the first and arranged toprovide communication between a liquid reservoir and the largedisplacement master cylinder when the piston of the same is in retractedposition. r

2. A power braking system for a tractor and trailer vehicle combinationcomprising brakes on the tractor, hydraulic means for operating thetractor brakes, brakes on the trailer, hydraulic means for operating thetrailer brakes, a master cylinder having a relatively large diameterbore connected to both of said hydraulic means, said master cylinderhaving sufficient displacement to operate both tractor and trailerbrakes, a power cylinder adapted to exert effort to displace fluid underpressure from said master cylinder, valve mechanism under the control ofthe operator for actuating said power cylinder, a relatively smalldiameter chamber having a piston therein which is operatively associatedwith the large diameter master cylinder whereby the pressure of liquidin said chamber exerts an effort which assists the power cylinder indisplacing fluid under pressure from said master cylinder and the volumeof the chamber increases proportionately o the decrease in volume .ofthe master cylinder during its applying stroke, and a manually operatedlow displacement master cylinder in communication with said chamber.

3. A power braking system for a tractor and trailer vehicle combination,comprising brakes on the tractor, hydraulic means for operating thetractor brakes, brakes on the trailer, hydraulic means for operating thetrailer brakes, a master cylinder having a relatively large effectivecross-sectional area and operatively connected to both of said hydraulicmeans, said master cylinder having suflicient displacement to operateboth tractor and trailer brakes, a power operated booster adapted toexert effort to displace fluid under pressure from said master cylinder,an operator operated low displacement master cylinder, valve mechanismcontrolling said booster and itself controlled by said operator opvolumeof the expansible chamber increases proportionately to the decrease involume of the master cylinder during its applying stroke, a compensatingpassage associated with a liquid reservoir and in communication with theoperator operated master cylinder when the piston of the same is inretracted position, and a second compensating passage independent of thefirst and arranged to provide communication between a liquid reservoirand the first-mentioned master cylinder when the piston of the same isin retracted position.

4. A power braking system for a tractor and trailer vehicle combinationcomprising brakes on the trailer, hydraulic means for operating thetrailer brakesa master cylnder mounted on the trailer and incommunication with said hydraulic trailer brake operating. means foractuating the same, a fluid reservoir mounted on the trailer and incommunication with the aforesaid master cylinder when the same is inreleased position, brakes on the tractor, hydraulic means for operatingthe tractor brakes, a second master cylinder mounted on the tractor andin communication with said hydraulic tractor brake operating means foractuating the same, said second master cylinder having a relativelylarge effective cross-sectional area, a motor operatively connected bymeans of a removable coupling to the trailer master cylinder and incommunication with said second master cylinder, said second mastercylinder displacing fluid to operate both tractor and trailer brakes, afluid reservoir adjacent said second master cylinder and incommunication with the some while it remains released, a power operatedbooster adapted to exert effort to displace fluid under pressure fromsaid'second master cylinder, an operator operated low displacementmaster cylinder on the tractor, a fluid reservoir adjacent said operatoroperated master cylinder and in communication with the same while itremains released, valve mechanism controlling said booster and itselfcontrolled by the displacement of fluid from said operator operatedmaster cylinder, and an expansible chamber in communication with theoperator operated master cylinder and having a relatively smalleffective cross-sectional area in relation to said second mastercylinder, said expansible chamber being operatively associatedwith saidsecond master cylinder whereby the pressure of liquid in the expansiblechamber exerts an effort which assists the booster in displacing fluidunder pressure from said second master cylinder and the volume of theexpansible' chamber increases proportionately with the decrease involume of said second master cylinder during its applying stroke.

R. PRICE.

